Increasing evidence points to a causative role for amyloid-beta peptide (Abeta) in the pathogenesis of Alzheimer's disease (AD). Thus, mechanisms through which Abeta affects cellular properties have come under intensive study. Higher concentrations of Abeta (1-40/42), present later in AD, form aggregates and fibrils capable of non-specifically damaging membranes of virtually any cell. Earlier in AD, when lower levels of Abeta are present, specific interactions of Abeta with particular cells, as well as sensitive subcellular loci, could also contribute importantly to induction of cell stress. We have identified a new member of the short-chain dehydrogenase/reductase family found in endoplasmic reticulum (ER) and mitochondria, termed Abeta Binding Alcohol Dehydrogenase (ABAD), whose unique features including Abeta in the nanomolar range, potentiation of Abeta-induced cell stress in vitro and in vivo, broad enzymatic activity, and increased expression in AD brain. Key pieces of preliminary data support a link between ABAD and Abeta- mediated cellular perturbation relevant to AD: in vitro, cells expressing ABAD and mutant betaAPP(V717G) displayed reactive oxygen relevant to AD: in vitro, cells expressing ABAD and mutant betaAPP(V717G)displayed reactive oxygen intermediates (ROIs), reactive aldehydes, induction of DNA fragmentation, and enhanced generation of Abeta. In intermediates (ROIs), reactive aldehydes, induction of DNA fragmentation, and enhanced generation of Abeta. In vivo, double transgenic mice with targeted expression of ABAD in neurons and mutant human amyloid precursor protein (hAPP) showed induction of cell stress markers (4-hydroxynonenal epitopes) and heme oxygenase type 1) and evidence of cytotoxicity, in contrast to observations in control animals. These data lead us to propose that the enzyme ABAD is a critical intracellular target potentiating Abeta- mediated cellular perturbation at the earliest stages of AD. Project 3 has the goal of determining whether over-expression of ABAD in vivo increase vulnerability to Abeta-mediated cellular dysfunction using transgenic (Tg) murine models. In view of increased levels of ABAD in neurons in AD brain and in vascular smooth muscle cells (SMC) IN Abeta-RICH vasculature, Tg mice with targeted over-expression of ABAD in neurons or vascular SMC will be crossbred with Tg mice over- expressing variant betaAPP. Mice will be analyzed according to pathologic and functional endpoints (electrophysiological, biochemical and behavioral parameters), as for their response to ischemic stress. Project will work closely with Project 1 2 & 4, and will obtain technical assistance from Core B. Collaborative interactions will include: exchange of reagents/techniques related to ABAD biology (Project 4), evaluation of cellular stress (Projects 1-2), and pathologic analysis (Core B).